Thrombin(s) has become among the best studied serine proteinases and has both enzymic (proteolytic) and nonenzymic (hormonal) bioregulatory functions in hemostasis, wound healing, and related physiologic processes. Some 10- to 20- million units of human Alpha-thrombin with high clotting and all other thrombin-ascribed activities continue to be produced in our laboratory annually for our own studies, as well as for those in other laboratories (U.S. and abroad). In addition to this form, we are making enzymically active forms lacking clotting activity (e.g., by autolytic, tryptic, elastolytic digestion) and enzymically inactivated forms posessing hormonal activities (e.g., by modification with i-Pr2P-F, D-Phe-Pro-Arg-Ch2-Cl) in order to map active-site regions and structural domains of thrombin required for enzymic and nonenzymic functions. We are also attempting to isolate hormonally active fragments (e.g., leucocyte proteinase digests), which might participate in post clotting events. Collaborative studies provide us with the ability to assess various biological activities (e.g., platelet responses, vascular endothelial monolayer permeability, leucocyte functions). Other collaborative studies will also include the evaluation of human (pro)thrombin recombinant gene products. Our extended laboratory approach is believed to have resulted in major contributions (e.g., the majority of materials for the recent Satellite Symposium of the Xth Congress of the ISTH on "Cellular Events Mediated by Thrombin and Related Proteinases" (San Diego, July 1985) and the New York Academy of Sciences Conference on "Bioregulatory Functions of Thrombin" (New York, February 5-7, 1986).